This invention relates to a plate leveller and more particularly to a plate leveller capable of levelling both light and heavy gauge plates.
Prior art plate levelling machines include a series of upper and lower banks of rolls arranged in a staggered relation to each other. The lower rolls are arranged generally tangentially to the path of material travel called the pass line. The upper rolls are arranged such that their distance from the pass line increases from the entry to the discharge sections. As the plate to be flattened is passed through prior art machines, it is initially distorted into a wave shaped configuration in the entry section. The magnitudes of the waves are gradually reduced as the plate passes through the machine so that it emerges from the delivery section in a flattened state. In the design of prior art machines, the roll diameter and spacing was selected to permit sufficient deflection of the product to produce a stress equal to the material yield strength through up to 85% of the plate thickness. The thickness range capability of prior art levelling machines was generally limited by constraints of selected roll diameter, spacing and load-carrying capability. In particular, small diameter relatively closely spaced rolls are required to process light gauge product. On the other hand, heavy gauge product requires relatively larger and more widely spaced rolls.